Foram avaliadas as taxas de reconcepção de 98 novilhas primíparas (34 Guzerá - G, 32, 1/2 Guzerá x 1/2 Nelore - GN e 32,1/2 Red Angus x 1/2 Nelore - AN) com 14 meses de idade e peso médio de aproximadamente 249,65kg, criadas em pastos de Brachiaria brizantha cv Marandu. Na segunda estação de monta (EM), foram utilizadas apenas as 36 primíparas gestantes na primeira EM (três G, nove GN e 24 AN), com média de idade de 26 meses e peso corporal de 313,67±25,01kg, 336,50±45,84kg e 399,86±44,45kg, respectivamente, para as fêmeas dos grupos G, GN e AN. O grupo AN apresentou ganho médio diário (GMD) de 0,30±0,06 (kg/dia) e maiores taxas (58,33) de reconcepção (P<0,05), comprovando que a heterose resultante do cruzamento entre raças distintas com maior distância genética (Bos taurus taurus x Bos taurus indicus) proporciona maior desempenho produtivo e reprodutivo.

This study aimed to evaluate the ultrastructural morphometry of bovine embryos produced in vitro grown at different concentrations of antioxidants. After in vitro maturation and fertilization, the presumptive zygotes were assigned into five treatments. T1) without the addition of any antioxidants (negative control); T2) addition of 50μM/mL cysteamine; and T3, T4 and T5) adding 2.5μg/mL, 5.0μg/mL or 10.0μg/mL of the antioxidants derived from the oily extract from Lippia origanoides, respectively. On D7 of culture, the embryos in the blastocyst stage were fixed and prepared for electron transmission microscopy. These were evaluated for the proportion of cytoplasm-to-nucleus, cytoplasm-to-mitochondria, cytoplasm-to-vacuoles, cytoplasm-to-autophagic vacuoles and cytoplasm-to-lipid droplets. Blastocysts cultured in media containing oily extract of Lippia origanoides presented morphological characteristics such as high cell:mitochondria ratio and low cell:vacuoles and cell:autophagic vacuole ratio, possibly been morphological indicators of embryonic quality. Inner cell mass (ICM) from blastocysts cultured in media without any antioxidants had the highest cell:vacuole ratio. Similar results were found in the trophectoderm (TE) cells of blastocysts from treatment 2. Embryo culture media supplemented with antioxidants derived from Lippia origanoides oil produced embryos with a higher cytoplasmic proportion of organelles, such as mitochondria. Also, treatments without any antioxidants or with the addition of cysteamine presented cytoplasmic vacuolization, a characteristic related to production of poor-quality embryos.

Culture of bovine embryos is a critical step during in vitro embryo production (IVEP) and, as such, has been the focus of numerous studies on cattle IVEP. Improvements of culture conditions to mimic the in vivo maternal microenvironment involves studying the optimal gas tension for pre-implantation embryonic development. In the commercial conditions, there is great variability in results, in part because of the difference between breeds and donors. The objective of this study was to evaluate the effects of culture in high or low oxygen tension upon the development of embryos from a crossbred dairy breed (Girolando F1; Gir × Holstein) and a beef Bos indicus breed, Nellore. We collected data from an IVEP commercial operation located in a tropical area of southeastern Brazil (Minas Gerais State) from February to May 2017. The study was designed in a 2 × 2 factorial arrangement of treatments: 2 O2 tensions during culture (5%, low O2 v. 20%, high O2) and 2 breeds (Nellore, beef v. Girolando F1, dairy). Thus, the following 4 groups were studied: Nellore-high O2 (n = 86 donors), Nellore-low O2 (n = 107 donors), Girolando F1-high O2 (n = 114 donors), and Girolando F1-low O2 (n = 110 donors). Outcome variables were the number of cleaved embryos 72 h post-insemination (hpi), cleavage rate relative to the total number cumulus–oocyte complexes (COC) put in culture, number and percentage of blastocysts 192 hpi relative to the structures kept in culture. Variables that were not normally distributed were transformed using the formula log(y + 0.05). Data were analysed using the GLM procedure of SAS (SAS Institute Inc., Cary, NC, USA) for the main effects of gas tension (low v. high O2) and breed (Girolando F1 v. Nelore). Results are shown as mean ± SEM. Gas tension affected the number of cleaved embryos (10.52 ± 0.92 v. 8.33 ± 0.72 for high and low O2, respectively; P < 0.01) and cleavage rates (40.58 ± 2.49 v. 44.41 ± 2.88 for high and low O2; P < 0.01 in Nellore), but did not affect these variables in Girolando F1 donors (13.23 ± 1.33 v. 10.76 ± 0.76 cleaved embryos, for high and low O2; P = 0.63; 58.01 ± 2.00 v. 60.19 ± 1.97 cleavage rate, for high and low O2; P = 0.80). Nonetheless, the number and percentage of blastocysts were not affected by gas tension in either breed. Results for Nellore were 4.99 ± 0.56 v. 3.51 ± 0.38 blastocysts in high and low O2, respectively (P = 0.051) and 41.92 ± 3.91% v. 39.81 ± 3.77% blastocysts, in high and low O2 (P = 0.11). For Girolando F1, numbers of blastocysts were 5.84 ± 0.66 v. 4.24 ± 0.39 in high and low O2 (P = 0.19) and percentage of blastocysts 49.14 ± 2.97% v. 49.11 ± 3.40% in high and low O2 (P = 0.46). These results suggest that oxygen tension during culture affects IVEP differently depending on breed. The initial period of culture, recognised as critical in IVEP, seemed more sensitive to high O2 tension, particularly in Nellore.

The aim of this study was to evaluate the supplementation of embryo culture medium with antioxidant obtained from oily extract of Lippia origanoides on in vitro blastocyst development and quality. Oocytes collected from slaughterhouse ovaries were matured and fertilized in vitro following standard laboratory procedures. Zygotes were cultured in SOF medium supplemented according to the following treatments: T1 embryo culture medium without antioxidant supplementation; T2)50μM/mL Cysteamine; T3)2.5μg/mL; T4)5.0μg/mL and T5)10.0μg/mL of antioxidant obtained from oily extract of Lippia origanoides. On the seventh day of culture, the blastocysts were fixed and evaluated for apoptosis rates, number of total cell and inner cell mass cells by means of the TUNEL Test. The use of antioxidants during cultivation did not increase (P> 0.05) the final blastocyst production rate. The treatments T2, T3, T4 and T5 had the lowest (P< 0.05) apoptotic indexes (4.5±1.1%, 8.4±2.5%, 3.4±1.1% and 5.5±0.9%, respectively) when compared to T1 treatment (10.0±1.4%). The number of inner cell mass did not differ (P> 0.05) among embryos from different treatments. The addition of antioxidant obtained from oily extract of Lippia origanoides reduces the apoptosis rate and improves the quality without increasing the total in vitro production of bovine embryos.